ABSTRACT
Today, plant disease control measures are highly significant due to the intimate relationship between plant health and the well-being of people, animals, and the environment (Harrington, 1995). To safely meet the food needs of the growing human population, we will have to continue to develop better management practices and sustainable plant disease management strategies. Plant diseases can significantly reduce crop yield and quality, and can also affect human and animal health through the accumulation of toxic residues in consumable products. Highly efficient, environmentally sound control strategies are therefore critical to the future of agriculture, with a strong empha sis on the need for biological-based approaches of disease man agement. Apart from being effective in controlling plant pathogens, biocontrol products should not negatively impact non-target organ isms (Brimner and Boland, 2003), or create tolerance development in pest organisms (Gossen and Rimmer, 2001). We should find ade quate and efficient alternatives to chemical pesticides with minimal environmental impact (Ekelund, Westergaard, and Soe, 2000). Of various potential pathways, arbuscular mycorrhizal (AM) fungi man agement has raised considerable interest in the sustainable agricul ture community (Bethlenfalvay and Linderman, 1992; Schreiner and
Bethlenfalvay, 1995). Mycorrhizas constitute the most important mutualistic symbioses on earth (Strack et al., 2003). The most com mon type, arbuscular mycorrhiza, develops in the roots of up to 80 percent of all terrestrial plant species and involves more than 150 spe cies of the Glomeromycota (SchiiBler, 2002). It is now well established that AM fungi exhibit no host specificity, but rather host preference. These soil organisms play key roles in the diversity and productivity of natural ecosystems’ (Hart and Klironomos, 2002; Hart, Reader, and Klironomos, 2003; van der Heijden et al., 1998), and are associated with most agricultural crops (Smith and Read, 1997). AM fungi are major components of the rhizosphere that can affect both the inci dence and severity of plant diseases in agriculture and horticulture. Several reviews and books have been published over the years, gener ally reporting on specific aspects of interactions between AM fungi and plant pathogens (Dehne, 1982; Garcia-Garrido and Ocampo, 2002; Graham, 1986; Linderman, 1992, 1994, 2000, 2001; Miller, Rajapakse, and Garber, 1986; Perrin, 1990, 1991; Schonbeck, 1979; Smith, 1988; St-Arnaud and Elsen, 2005; St-Amaud, Hamel, Caron, and Fortin, 1995). The purpose of the present chapter is to summarize the research on various agricultural crops, with particular emphasis on the modes of action through which AM fungi could reduce plant disease damage in agriculture.
